sched: Fix cfs_bandwidth misuse of hrtimer_expires_remaining
hrtimer_expires_remaining does not take internal hrtimer locks and thus must be guarded against concurrent __hrtimer_start_range_ns (but returning HRTIMER_RESTART is safe). Use cfs_b->lock to make it safe. Signed-off-by: Ben Segall <bsegall@google.com> Signed-off-by: Peter Zijlstra <peterz@infradead.org> Cc: pjt@google.com Link: http://lkml.kernel.org/r/20131016181617.22647.73829.stgit@sword-of-the-dawn.mtv.corp.google.com Signed-off-by: Ingo Molnar <mingo@kernel.org>
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@ -3285,7 +3285,13 @@ static const u64 min_bandwidth_expiration = 2 * NSEC_PER_MSEC;
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/* how long we wait to gather additional slack before distributing */
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/* how long we wait to gather additional slack before distributing */
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static const u64 cfs_bandwidth_slack_period = 5 * NSEC_PER_MSEC;
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static const u64 cfs_bandwidth_slack_period = 5 * NSEC_PER_MSEC;
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/* are we near the end of the current quota period? */
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/*
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* Are we near the end of the current quota period?
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*
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* Requires cfs_b->lock for hrtimer_expires_remaining to be safe against the
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* hrtimer base being cleared by __hrtimer_start_range_ns. In the case of
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* migrate_hrtimers, base is never cleared, so we are fine.
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*/
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static int runtime_refresh_within(struct cfs_bandwidth *cfs_b, u64 min_expire)
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static int runtime_refresh_within(struct cfs_bandwidth *cfs_b, u64 min_expire)
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{
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{
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struct hrtimer *refresh_timer = &cfs_b->period_timer;
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struct hrtimer *refresh_timer = &cfs_b->period_timer;
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@ -3361,10 +3367,12 @@ static void do_sched_cfs_slack_timer(struct cfs_bandwidth *cfs_b)
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u64 expires;
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u64 expires;
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/* confirm we're still not at a refresh boundary */
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/* confirm we're still not at a refresh boundary */
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if (runtime_refresh_within(cfs_b, min_bandwidth_expiration))
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return;
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raw_spin_lock(&cfs_b->lock);
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raw_spin_lock(&cfs_b->lock);
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if (runtime_refresh_within(cfs_b, min_bandwidth_expiration)) {
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raw_spin_unlock(&cfs_b->lock);
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return;
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}
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if (cfs_b->quota != RUNTIME_INF && cfs_b->runtime > slice) {
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if (cfs_b->quota != RUNTIME_INF && cfs_b->runtime > slice) {
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runtime = cfs_b->runtime;
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runtime = cfs_b->runtime;
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cfs_b->runtime = 0;
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cfs_b->runtime = 0;
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